The field of art to which this invention pertains is synthetic resins containing a hydrophilic group, said resins being soluble or dispersible in water when salted.
Industrial coating processes utilizing aqueous dispersions or solutions of organic resinous film forming compositions continue to grow in importance. Aqueous coating compositions are used in various applications, such as spray coating, flow coating, and electrodeposition coating processes. Particularly useful organic resinous film forming compositions are cationic compositions which, primarily, are used in primer paints for metals. Such cationic compositions which contain amine nitrogen groups have superior corrosion resistance when formulated into primer paints. Particularly useful examples of cationic sinous compositions are the reaction products of polyepoxide resins and amines.
British Pat. No. 873,264 and U.S. Pat. No. 3,321,548 describe adducts of epoxy resins and primary or secondary amines, said adducts being useful as coating compositions when dissolved in organic solvents and subsequently crosslinked with polyisocyanates. In the adduct formation reaction, the primary amine reacts with an epoxy group of the epoxy resin to form a secondary amine group which is attached to the epoxy resin molecule plus a pendant hydroxyl group. In the same manner, the secondary amine reacts to form a tertiary amine group and a hydroxyl group.
U.S. Pat. No. 3,984,299 is representative of a number of patents which describe aqueous coating compositions made from adducts of epoxy resins and primary or secondary amines, said adducts being salted with acids to render them water soluble or water dispersible. The reaction involved in adduct formation is the same as described in the preceding paragraph.
U.S. Pat. Nos. 3,962,165 and 4,101,486 are representative of a number of patents which describe the reaction of epoxy resins and tertiary amine-acid salts to form resins which contain quaternary ammonium groups. Such resins are soluble in water and are useful as coating compositions.
Canadian Pat. No. 884,929 describes ungelled epoxy-containing reaction products of epoxy resins and amines wherein the amine contains one or more secondary or tertiary amino groups and at least one hydroxyl group. It is pointed out in the patent that the nature of the reaction product is not known with certainty and that several reactions may be involved. One postulated reaction is the reaction of the hydroxyl group of the amine with an epoxy group. It is also suggested that the amine group may either react with or initiate interreaction between epoxy groups.